Method and apparatus for making hollow rubber articles



March 2 `1926.

F. T. ROBERTS METHOD AND APPARATUS FOR MAKING HOLLOW RUBBER ARTICLES'Filed oct. 1e. '192:2A

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. ATYs.

March 2 1926.

F. T. ROBERTS MTHOD AND APPARATUS FOR MAKING H OLLOW RUBBER ARTICLESFiled Oct. 16, 1922 3 Sheets-*Sheet 2 `ATTY3 March 2 1.926.

' F. T. ROBERTS METHOD Aub APPARATUS FOR MAKING HoLLow RUBBER'ARTICLESFiled Oct. 16. 1922 3 Sheets-Sheet' MM45 up; mx', ATTYS @nf Wam lAvmLALB COPY Patented Mar. 2, 1.926. i

QUH'S 'EUBEBMSE N 0E REPWABE surroundl-ng sttmpsp l r of the sheetssurrounding the cavities, are' j of transferring the articles fromforming to vulcanizing molds. It also eliminates the step ofentrappingcompressed air as formerly used in myprocess above referred to.

While the preferred method and best advantage derived from this methodis by forming, joining and `vulcanizing the parts of the article in thesame mold, a similar result can be accomplished, though not asetiiciently, by forming the parts of the articles in mold members,transferring them to other molds and joining them together in thesemolds, and either vulcanizing them in the molds used for joining, orusing other molds for vulcanizing purposes.

The formed parts may also be joined together in cavities of the propersize set between an ordinary punch press'or any rotary machine, and thenmay be removed from these joining molds to any suitable type ofvulcanizing molds, and, in this case, after the parts ofthe article arejoined together they may be placed in the curing molds with the seamson` the same planeas the face of the mold or with the seams crosswise. Y

Still other specific objects include the construction of the male andfemale mold members to provide for effective cutting off of the surplusstock around the mold, and at the same time rovide a joint between thelcavities of sufficient width to securely hold the article against theinternal vulcan izing pressure. I may buff off the edges of the formedparts of the article by the passing of a rapidly revolving buing rolleracross the tops ofthe mold cavities. thus producing a roughened surfaceof uniform height on the edges of' each hemisphere, or other formedhalves. By similar means, if desired, I may treat the edges withvulcan-A j izing cement.

The above and other objects are made. more fully apparent in connectionwith the illustrative apparatus, by which I carry out` the process ofthe present invention, and to which the following description refers.

In the drawings, Fig. 1 is a vertical sec- -tional view through the moldmembers shown as carried by a suitable press for bringing them togetherand illustrating raw rubber pellets, from which the parts of the articleare formed, in position in the cavities; Fig. 2 is an enlarged sectionalview Q f these same mold members; Fig. 3 is a forming -plateprovidedwith protubcranccs at either side thereof; Fig 7 is aperspective of the forming plate; Fig. 8 is an in side plan of either ofthe halves of thc forming plate; Fig. 9 is an elevation*illustratingmore or less iagrammatically a carrier for moving mold lates with thearticles therein 'under a buffmg roll; Fig. 10 shows the press membersbrought together with the intermediate male members removed; Fig. 11 isan enlarged detail of theV mold meinbers inthis position, showing thearticle with .its chemical pellet to create the internal pressure eitherin this press or` a separate vulcanizer, and Fig. 12 illustrates aseparate vulcanizing chamber containing a number of the mold memberslocked tovgether after removal from thepress.

Referring to the drawings'. by .the use of reference numerals, 1 and -2indicate the lower and upper mold members-'provided with cavities, whichin thease of balls, are preferably hemispherical i each mold, thesurface of the molds are cut awfay around the cavities leaving the ribs4 narrow enough to form cutting edges, and' yet of suicient width toform meeting surfaces when the molds are together.

These mold members may beheld in position by any suitable means. I haveshown side rails engaged by clamps 6 upon platens 8 and 9, of ahydraulic press; the platen. 8 being movable toward and away from thcstationary platen by a plunger 10 and guided by the vertical rods 11 towhich t-he upper platen is rigidly secured. Dowel pins 12- serve tocause accurate registration of the mold members. Suitable means areemployed for heating the molds 1 and 2, as for instance by providingsteam spaces 13 and 14 in the respective platens, with which communicatesuitable piping indicated at. 7 for conveying steam to andfrom theplatens.

An intermediate forming mold member l is shown as consisting of ahorizontal body l5 provided with protuberances 16 and 17 adapted toproject into the cavities of the plates 1 and 2. These projections areshown as slightly smaller` than the cavities. and they are surrounded byannular ribs 1Sl wh ch coact with the ribs 4 surrounding the cavities,thereby serving as cutting edges to sever the surplus stock or trim fromthe article parts formed in the mold luembea vrods 11 and is supportedwhen not in use bykeys 19 engaging slots in therods.

The intermediate formin member is made hollow and provided with steamconnections so that 1t may be readily maintained-hot. As a convenientWay to eilect t-his, I make the member oftwo correspondlates 50, shownseparatedin Flg. 8, whic plates are secured together, and I form theprotuberances as separate hollow inserts mounted in these plates.` Morespecifically, each plate 50 has holes 51 drilled through it, these holesbeingv consemi-curing" is 5 the mold and forming members ifldesired.

.ing to and from the grooves vin Y provide for keeping the plates hot.

nect'ed by grooves 52. 4Two plates so ar-` ranged are placedf'lface toface upon an in-v termediate mar inal gasket 53 which may seat in aslight y cut down portion ofthe plates and then these plates are broughttight together to compress the gasket and are'held by suitable means, as`for instance the screws 54,Ythe portions of the plate between thegrooves 52 abutting each other. Ihe protuberant inserts may have clindrical Walls '55 and these are force by pressure snugly into thecylindrical openmgs in the plates!` The inserts have in their basesgrooves 56 communicating with Y their hollovtT interiors 57 andregistering with the grooves 52 in the holding members. Suitable steamconnections 59` leadthe plates It will `be understood that bymaintaining the mold members andthe intermediate forming member hot, Islightly vulcanize` or senil-cure the rubber; stock in the samelcavities in which they areformed. Such articlesto hol their sh`ape,\anddoes not interfere `with `their subsequent complete cavities andpipingalsor enable water to be subsequently passed into the parts tocool Vithin thecavities, `I have shown (in case, the hemispheres. Theserubber slugs may be readilyiformed by accurately cutting ofrpredetermined short lengths of rubber from a continuous cylinderformed' Y on a tubing machine. yThe :slugs or ellets or rubber,designated It, are fs Ightly against the `mold cavity "when placed,`thus causing them to adhere slightly, whereuponv 4the three-part mold pmembers brought together'in the'pressfthus forcing may be "the vrubberto yfill the `hemispherical cavi- :ties between the male and femalesurfaces.

' As the parts ofthe mold are lcaused tov meet along the ribs 1,4"a'nd'18, thef surplus Arubber is severed or trimmedfrom that in thecavities.' This position of the mold and the severmg 0f the rubber 1Slllstrated 1n cavities.

gust suiicient "to cause VYthe Y n `application ofv 1 a slide and a'cernen vulcanization` to form -a tight seam. The

' `rubber or trimY islremovedand saved.

Vhen the molds are se arated toI remove the forming 'platetherulbbervtends to adhere to the cavities, and toassur'e this I may cover the,forming parts 17 with soft soap or soap stone. 1 Y The mold Vmembers 1andi?l brought together causing theedgesof the hemispheres to unite. YTheprotuberances 17 are surrounded'Ylby 'channels inside vof the ribs 18which allows the rubber formed in the cavities to"project slightlyout-ofthe These projecting edgt'gesfm' Y be accurately Ybufed off toprepare-,th es for uniting, andl avoidfthe "possibility `of `anydistortion of the rubber at the seam? Y` vThe means for buiiingffoiithissurplus rubber and preparingthe` edgesof the hemispheres may be ajdevice 'such' as lillustrated in Fig. 9 wherein lla* slide 20-"ismounted on may then Ibe a frame 21, andy rovided with r'suitable theedges of the hemispheres H"projectingl therefrom asshown 'at VE, -th'ebuing roll may be caused to remove the v'surplusrubber substantially"down `to 'the' ribs.V 4, `thus preplying vulcanizing cement? assuringa; more perfect unio'n' atthe seam. If'ldesired, this cement* may4 be,made [by Y such r applying-'w114 so that the applicationofementimaytake 4lace 'atr once in allfof the, partsfin-one o vthe molds"with"themembers` therein as'itis moved under "the roll.l Y The-mold`members p v l `may nowfbe replacedA in vafpress like that Figs. 1 and2)lthe -raw`rubberj stock which `is to form the article parts, in thepresent of Fig.V 1 witlioutithepla'te 15 as'fsliown in Fig. 10." Theparts are-now-irmlyf pressed togethercausing the surface-ofgtheribs 4 totightly meetlandcausingtheiedgeslof the hemispheres tof Yuu'rite;*Before* bringing these parts together; avslitz'iblechemical `,is placedwithin-the fa'rtio'les be clamped* together 'and transferredto "a uch fclamping if Vmay en fle lwedgelm'embers Ysentng aneven'but` roughenededge'lon the Y a steam-tight chamber 40, supplied by steam through asteam controlled passage or pipe 41 and' provided with suitable outlet42. The front of the chamber may be closed by a removable cover on thedoor 44 and clamped by a screw 45 provided with a sultable hand wheel,the screw extendin through a yoke 46 ivotally secured at 4 to the frameof the c iamber, and adapted' to be locked bya suitable pin or otherremovable means as at 48.`

Instead of using the pellets or slugs, I' may use sheets of raw rubberas shown at S in Fig. 3, one sheet being laid over the mold member 1 andthe other on top of the projections 17 of the forming mold mem. ber 16,afterwhich these 'parts are brought together to the position shown inFig. 4. The-result of. forming the hemispheres being the same as before.After separation of the members the hemispheres remain in the cavitiesand the surplus of. the sheets are simply removed and may be reused. Tocause the hemispheres to hold ,their shape and position in the molds, Iprefer' to slightly cure them by the expedient of previously heating themold members 1 and 2. before placing the rubber thereon. Thus when thesheets or slugs are placed in positionvand these hot mold membersbrought together, the rubber in the cavities is very tightly compressed,rendering the (parts forming the walls of articles very ense, ascompared to the stretching of the rubber into itsjseat which occurs whenfully or 4partially seating the rubber by a. vacuum.

- This stretching naturally causes something of a separation of themolecules and renders the rubber more porous. When the parts are broughttogether, they are held there momentarily, under pressure, and themoldmembers being hot gives'the rubber in the 'mold members something of aslight cure,- just enough to cause the rubber to hold its shape. Thetrim of the rubber of the surplus is not materially effected by thisheat and therefore is not damaged for reuse.

In carrying out my process to comply with all of the requirements ofaccuracy,

uniformity, etc., of the nal results when making balls, such as tennisballs, for example, one of the important things is to create an internalpressure in each ball of exactly the amount desired. By my method thispressure serves to maintain. the articles or balls distended duringvulcanization and thereafter affords the permanent internal pressureproviding the resilience for playing purposes. This pressure is obtainedby the use of a chemicalsubstance adapted to generate a permanent gas,when subjected to the curing heat, and I desire to use the chemical insuch form that accurate amounts may be placed within the articles withthe greatest convenience. To this end, I may em loy a mixture generatinga nitrogen gas, or ex# ample, according to the following formula:

I prefer to make an accurate mixture of this chemical in a suitablequantity and form Y l l'of these pills, indicated at '60 .in Figi 10,

within the rubber-lined cavities. Now upon the application of curing.heat,'the chemical actionvtakes place generatin Athe gas which remainspermanent at a pre etermmed pressure. As the walls of the article havebeen rendered denseby the formation pressure and the slight curing giventhem, as described, they remain dense throughout the vulcanization andthus retain the internal pressure over a longer period of time than ispossible in the absenceof this formation of the walls of the articleunder pressure.

V Summarizing the use of my apparatus, and steps of meprocesml firstplace sheets or slugs of rub r R as illustrated in Figs. 2 and 3 in themolds which have been previously heated by suitable means. 'lhe moldsare then brought together with a press, such as shown in Fig. 1. Therubber is'caused to fill the cavities between the male and femalemembers and the surplus is severed by the meeting edges 4 and 18, andthe parts are held in this position long enough for the heat of themolds to give the rubber a set while under this mechanical pressure. Themolds are then separated and the protruding edges of the hemispheres maybe bufed to facilitate the uniting of the edges, the buiing beingreadily accompllshed by the molds with the rubber therein are passed bythe use of movin slide or ycarrier 20'of the device shown in 9. Theedges may be other Wise prepared to assure a more completeunionifdesired, although the necessity for this depends upon the natureof the rubber used. Before bringing the parts together the gasgenerating pills 60 are placed, one in eachlower cavity. The` mold partsare now brought together in the press as shown in Fig. 10, where theedges 4 meet on a surface of sufficient width, being slightly wider thanas though it were a cutting edge only, to effectively close the cavityin which the article is held, so that the internal pressure generated bythe curing heat may not distort the ball or cause any fins thereon atthe meetin edges. After a suitable curing period, the alls are removedfrom the moles and may be suitably treated to complete the the revolvingroller under which a article, for example, by placingthe usual feltcover thereon for use as a tennis ball.

Thus by my process, I am enabled by very simple vand effective series ofsteps to form articles under mechanical pressure, give them a slightvulcanization, which is ypreterably less than the usual semi-cure, thenretain them -in the same mold and 4cause them to unite to complete thearticle and therem after vulcanize the article with or without removalfrom these molds. Thus the parts of such a hollowarticlefhavingpermanent inlation are formed and united in the same mold,and various advantages result, not only in-'accomplishing economy, but Iam enabled to produce a superior article. l I claim l. A method ofmaking permanently in- Hated hollow rubber articles, consisting ofvslightly vulcanizin rubber composition, while mechanically orming theWalls of the article under pressure and of continuously holding thearticles in the same mold member, uniting them and vulcanizing` themwhile giving them a permanent inllation.

2. A method Of'making permanently inlated vhollow rubber articles,consisting of slightly vulcanizing the rubber composition duringmechanical formation of the walls of the article under pressure and'while continuously holding themin the same mold member, uniting them andvulcanizing and giving them a permanent inflation.

3. The method of making hollow rubber articles consisting of slightlyvulcanizing a rubber composition during mechanical formation of the'walls of the article under pressure, and completing'thevulcanization iwithout removing from these molds.

4. The method of making hollow rubber articles consisting of formingpartsfot the wall of the article in molds having male and femaleportions pressed together onto the rubber stock, heating both surfacesof the rubber while so held, removing the male portion and bringing themold members iaving the parts therein together to unite the parts attheir edges, and then vulcanizing them while so held. p i 5. The stepsin the process of making hol-l low rubberarticles comprising shapingthe.desired article from unvulcanized stock in a mold heat-ed sutlicientlyto slightly vulcanize the formed part, bringing theparts of the article,together in the molds in which they were formed to unite them edge to-edge and subsequently vulcanizing the article.

6. The method of making hollow rubber articles consisting of forming theparts: of the article in mold members having male and` female portions,forming tne raw rubber? stock to the desired shape under pressure,vremoving the male portions and bulling the edges of the article while inthe cavity and thereafter uniting the article parts and vulcanizingthem.

* 7.-The method of making hollow rubber articles consisting of shapingthe article fromunvulcanized stock by the use of heated mold and' coremembers, removing the core', retaining the shaped parts'in the moldsockets and unitinr the ed es of the parts and v lcanizing the artic esin the same mold.

8. The method of; making hollow rubber articles consisting of shapingtwoor more `part-s of the article with mold and core members underpronounced mechanical pressure, at the same time heating the shapedparts sufficientl whereby they li the shaped parts inv the mold sockets,re-

to slightly vulcanize them i old their shape, retaining moving the coremembers, placing a gasforming chemical within the article to create avulcanizmg pressure, vulcanizing thev artlcles in the same mold sockets,and retaining a permanent pressure therein.

9. The method of making hollow rubber articles consisting of completelylshaping two parts of an article in mold sockets with mold cores,forcing the stock in shape and seating it in cavities, buiiing the edgesof the parts While in' the cavities, charging the interior of thearticlewith material to produce an inflating gaseous medium, bringing the partsof the article together, and vulcanizing the article in the' samecavities in which they are formed, and retaining the aseous mediumtherein.

10.` The met od of making hollow rubber articles comprising shaping twoparts of an article by seating it in'l cavities, bufing the edges of thearticle parts while in thecavities andthereafter bring the cavitarymembers together to join the parts ofthe article.

11. `The method of making hollow rubber articles comprising shaping twoparts of an article bseatin sufficient y 'to ma e it hold its shape,butling the edgesof the article parts while in the it in` cavities,heating itv cavities, and thereafter bringing the cavitaryfk memberstogether to join-the parts of the article. f t

12.` The method of making hollow rubber articles comprising mechanicallyf forcing raw rubberstock into mol-d sockets, heating the stock while inthe sockets sufficiently to makeit retain its shape, buiiing the. edgesof the said arts while in the sockets, there- ,after bringing thepartstogether to join other, and thereafter vulcanizi them' to each ingthe'article.

. ,13. The method of making hollow rubber articles consisting ofshapingthe4 desired .article of unvulcanized stock in -the mold bytheuse of cores, mechanically forcingthe Stockto shape underpressure,'removing the cores, bufiing the edges of the article while inthe mold sockets, and uniting the shaped fparts of the-article andvulcanizing them in while in the same cavities.

the same mold sockets.

14. The-method of`makng hollow rubber articles consisting of shapingthearticle into two parts in mold cavities b the use of complementary moldwcores, orcing unvulcanized .stock lin the cavities to shape, slightlyvulcanizing the article parts while held under pressure, removing thecores and then uniting and vulcanizing the article 15.y The method ofmakinghollowfrubb'er articles consisting of shaping the article in partsin mold cavities by the use of comlementary mold cores, consisting of,iirst eating the mold members so that as the unvulcanized stock isforced to its seat and held, it becomes vulcanized to a slight degreesuicient to hold its sha e, removing the coremembers, completing t evulcanizatio-n while held in the original cavities and simultaneouslycreating an internal pressure inthe article. 16. The process of articlesfrom continuous consisting of forming the articles of two arts, each inmold cavities b the use of lntermediate mold members aving protuberancescomplimenta to the cavity hollow rubber pressed into the cavity byringing the mold parts together upon the v protuberances underV ressuresuihcient to firmly seat the v forme Vparts inthe cavity andfto sheerthe surplus rubber from around the cavities,

'heating the intermediate mold member to effect a slight vulcanizationof the rubber stock removing the intermediate mold member and thenremovin the surplus rubber from around the mol cavities, buing the edgesof the formed parts placing a mixture which will produce a permanentgasinto the formed parts, joining the formed parts together bymechanical pressure while in mold members and thereafter vulcanizingfthe hollow rubber article.

17. The process of making hollow rubber articles consisting of seatingraw rubber I stock in coacting mold members by the use of cores, forcingthe stock to its seat, previously heating the mold-members so that whenthe stock is forced to its seat under pressure it is causedto comvr leteits formation and bevulcanized slig tl and thereafter removin the coremem and the rubber trim, placing a chemical pellet within one of theparts, bringing'the parts together without removal from the cavities andthen vulcanizing the article while in the same cavities.

18. The process of making hollow rubber articles consisting of shapingthe article from unvulcanized stock by the use of mold and core membersin which the core members are coated to prevent adhesion of the rubberstock thereto, fully forming and seat- Y. same time' heat' members andcore members,

thereto, adapted to'force lthe rubber stoc at sheet stock,

. stock, and

ammassi ing the stock in said core members, at the said stock to'slightly vulcanize it and t ereby fix its shape and removing the coremembers leaving the stock in the mold sockets'by adhesion of the rubberthereto, bringing the formed parts together and com letmg vulcanizationwhile in these same soc ets.

A19..An a paratus for making hollowrubber., artic es, consisting ofcavitary mold to its seat, and coacting means othecore members and moldmembers for severing the sur'plus stock from the parts formed in thecavities, and means for supplying heat to the mold members and 'coremembers.

20. In an apparatus of the character described, the combination of :apain of cavitar mold members, adapte to register with the -cavities andforce stock to its seat 1n the cavities wmcomplementari eorev memberspleting'its formation, and coacting ineens surrounding the icavities andcore'members for severing the sur' lus stock, means for'v conveyingsteam to t e interior 'of the core members, said coacting means' fqrmingmeeting edges to completely .enclose the article after the coremembers'are removed and the mold members brought together. to`

unite the., edges of the article.

21. An a paratus rubber artic es, consisting of cavitary mold members,coacting core members to 'form raw rubber stock by mechanical pressurefor forming A hollow Ain the' cavities, means for severing the surplusstock, and means for buing the edges of the articles while in thecavitles.

22. An apparatus for use in the manubeing means w flow to the interior othe core members. 24. A core member for forcing rubber stock to its seatirl/opposed cavities, consisting of a plate-havin a series of oppositerotuberances, means or conducting heating uid to the interior' of theprotuberances tuberances for severing .the trim 0f the stock.

force it to its seat, there. ereby. heating iluid may forming' hollowrubber .and means on the plate around the pro- 1 25. A pair of coacting'mold members vhaving cavities for the formation of parts of hollowrubber articles, acore member consisting of a plate having opposed protuberances, ,adapted to project into the cavities when the mold membersand core members are brought together, means for conducting heatingfluid to the interior of v the vprotuberances there being'cutting edges'on all three members wherebythe trim of the stock may be severed whenbeing formed, Jthe edges ofthe mold members meeting 'when the moldmembers are brought tof gether. f

26. A mold and core for `forming hollow rubber articles consisting of apair of cavity r conduit intheinterior of the intermediate memberwhereby heating fluid may be conducted to the interior.`

\27. A mold and Core member for forming hollow rubber'articles,consisting of a hemispherical cavity and a hemispherieal core, slightlyrsmaller than the cavity, a cutting edge formed around the cavity andaeut- 'ting edge formedv around the base of the core and slightlyspaced.therefrom by a channehsaid edgesb'eing adapted tomeet when these partsare brought together to form an article, there being means forconducting heating liuidto the interior of the core. c,

28'. The method of making permanently inflated hollow rubber articlesyconsisting of slightly vulcanized rubber while mechanically forming thewalls of composition the article under pressure in mold cavities t andwhile holdingthe formed parts of the article 'in mold cavities,introdpcing a chemical composition before uniting. the parts,

then uniting the formed parts by 'mechanical pressure andl vulcanizingthe joined parts, thereby producing permanents inflation from thechemical composition.

In testimony whereof, I hereunto alix my signature.V A

- FRED THOMAS ROBERTS.

